1. Field of the Invention
This disclosure relates to a method of fabricating a thin film solar cell and an apparatus for fabricating a thin film solar cell.
2. Description of the Related Art
A solar cell converts solar energy into electrical energy. The solar cell, which includes a diode generally having PN junctions, can be classified into various compositional types of solar cell depending upon the composition of the material used to form the light absorbing layer.
A solar cell including a light absorbing layer of silicon may be subclassified as either a crystalline substrate (wafer) solar cell or a thin film (amorphous, polycrystalline) solar cell. In addition, a compound thin film solar cell based on a CIGS (CuInGaSe2) or CdTe material, a Group III-V solar cell, a dye-sensitive solar cell, and an organic solar cell may each be exemplified as representative solar cells.
Of these, the thin film solar cell which includes a light absorbing layer of CIGS or CdTe further includes a buffer layer of CdS between the light absorbing layer and an adjacent electrode, to compensate for a band gap difference and a lattice constant difference. The buffer layer is prepared in accordance with a chemical bath deposition (“CBD”) process. A CBD process may include dissolving, for example, a cadmium (Cd) source material and a sulfur (S) source material in an ammonia solution, immersing a substrate formed to have a light absorbing layer therein to coat the substrate, and heating the coated substrate to provide a buffer layer having a thickness of several tens of nm. However, the CBD process undesirably increases the process cost and causes environmental contamination due to its requirement of large quantities of hazardous chemicals.